Apparently Marvin Jones has been playing with some significant injuries in one of the most important part of a wide receiver's body. Jones tweeted that he has torn finger ligaments for the past three weeks after the game, which you'd have to guess can hinder his ability to catch the football despite what Jones may argue to the contrary.
Jones has performed fairly well as Keenan Allen's partner-in-crime, hauling in 35 catches for 530 yards, and combined they're probably the most potent duo in the country. Jones and Allen have struggled with hanging onto the football at times, partly due to accuracy issues by Zach Maynard, partly due to their own mental errors, and it looks like Jones has an injury to fall back on when you lament his drops.
Don't expect this injury to significantly impact how much time Jones sees on the field. He's been able to play at a high level with the injury, and he should continue to be one of the top two options even with the occasional drop.
For more on the state of Cal football, go to the California Golden Blogs.